Fix issue 2589

[JustusAdam]

Description of changes:

This addresses #2589 by providing a better error message that contains both the trait that failed to resolve and the type which does not implement it.

Before:

error: internal compiler error: kani-compiler/src/kani_middle/reachability.rs:471:29: Unexpected polymorphic constant: Unevaluated(UnevaluatedConst { def: DefId(0:6 ~ issue_2589[1b49]::Dummy::TRUE), args: [Adt(std::string::String, [])], promoted: None }, bool) Unevaluated(UnevaluatedConst { def: DefId(0:6 ~ issue_2589[1b49]::Dummy::TRUE), args: [T/#0], promoted: None }, bool)

thread 'rustc' panicked at /rustc/65ea825f4021eaf77f1b25139969712d65b435a4/compiler/rustc_errors/src/lib.rs:995:33:
Box<dyn Any>
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Kani unexpectedly panicked during compilation.
Please file an issue here: https://github.com/model-checking/kani/issues/new?labels=bug&template=bug_report.md

[Kani] no current codegen item.
[Kani] no current codegen location.
error: aborting due to previous error; 1 warning emitted

After:

error: Type `std::string::String` does not implement trait `Dummy`. This is likely because `original` is used as a stub but its generic bounds are not being met.

error: aborting due to previous error; 1 warning emitted

Resolved issues:

Resolves #2589

Related RFC:

Optional #ISSUE-NUMBER.

Call-outs:

Testing:

• How is this change tested?

• Is this a refactor change?

Checklist

• Each commit message has a non-empty body, explaining why the change was made
• Methods or procedures are documented
• Regression or unit tests are included, or existing tests cover the modified code
• My PR is restricted to a single feature or bugfix

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 and MIT licenses.

[feliperodri]

LGTM.